Change default fopen() on Windows from fopen_s() to fsopen(,,_SH_DENYNO).

Change default fopen() on Windows from fopen_s() to fsopen(,,_SH_DENYNO).
fopen_s() won't let you open a file that is open by another process. This
has the unfortunate property of triggering a race condition in Python
exposed by running run-webkit-tests using a lot of threads and spawning
off image_diff. There doesn't seem to be a good reason to disallow files
that are open in other processes, so I'm changing this.

    BUG=none
    TEST=run_webkit_tests doesn't produce "image_diff: can't open file" errors
    R=darin@chromium.org

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=40710

[darin (slow to review), 2010-03-04 07:26:08]

LGTM